I have had boxes where I have not found a 40%, 90%, proof, or even a no FG. I have also had boxes that were 75% 1971. In my opinion, your box was a success - you found 1 silver and 2 other decent coins.
man, that's a disspointment for sure, i would think the box would have at least 10 silvers considering the ender rule which means for every ender, there should be 10 silvers...
hh
buff
p.s. usually for every ender I average 6-8 silvers, but once I had 1 ender and got 16 silvers, you never know.
Ya that or drive half an hour out of your way to pick up a 1000 bag of half dollars because the bank had them available that day and was gonna ship them out and go through them just to find out that they were probably someone's dump. Not fun